Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 12 2024 15:39:07 AWUS01 KWNH 121539 FFGMPD MDZ000-VAZ000-NCZ000-SCZ000-122100- Mesoscale Precipitation Discussion 0611 NWS Weather Prediction Center College Park MD 1138 AM EDT Fri Jul 12 2024 Areas affected...Northeast South Carolina through the DelMarVa Peninsula Concerning...Heavy rainfall...Flash flooding possible Valid 121536Z - 122100Z Summary...Showers and thunderstorms will expand in coverage and intensify through the afternoon. Rainfall rates of 2-3"/hr are possible, which through training will likely result in 2-3" of rain, with narrow corridors of up to 5" possible. This could cause instances of flash flooding, especially in urban areas. Discussion...GOES_E WV imagery this morning clearly indicates the favorable setup for heavy rainfall today. An extremely moist ribbon of air draped from SC through the Mid-Atlantic continues to stream northward, while shortwave impulses over the Atlantic spread north/northwest. PWs as measured by GPS are as high as 2.25", coincident with SPC RAP analyzed MLCAPE of 3000 J/kg, highest from the Grand Strand to the Outer Banks. Low-level S/SE flow of 15-25 kts at 850mb is drawing this moisture/instability overlap northward to supply impressive thermodynamics into a stationary front analyzed by WPC. The overlap of isentropic ascent atop this boundary, with convergence along the front, and additional convergence where the 850mb winds decrease and veer north of the associated trough will continue to drive pronounced ascent through the aftn. Rainfall rates estimated by local WSR-88Ds have already reached 1.5-2"/hr, and it is expected these will continue to intensify through the day. The stationary front is progged to waver back to the west as the most impressive advection of moisture (IVT nearing 500 kg/m/s) pushes into NC/VA. Not only will this continue to support near record PWs, but will also push the best thermodynamics westward towards the Piedmont. This suggests that convection will become more widespread, which is indicated by the available CAMs as well, leading to expansive coverage of rainfall rates which have a 20% (40%) chance of exceeding 2"/hr on the HREF (REFS). Mean cloud layer winds of 10-15 kts suggest storms will generally move to the north and along the boundary, with anti-parallel Corfidi vectors suggesting enhanced backbuilding and training as well. Where the most significant training can occur, which is likely to be in the immediate vicinity of this stationary front, total rainfall of 2-3" is likely, with a 20-30% chance of more than 5" also present in both ensemble systems (HREF/REFS). Although there is some spread in the CAM output, there appears to be a region of slightly higher potential for this maximum rainfall along and just west of I-95 across NC and into the Middle-Neck of VA where HREF EAS probabilities are greatest. While much of the Mid-Atlantic has been very dry noted by 7-day AHPS rainfall departures less than 50% of normal yielding elevated 3-hr FFG of 2.5-3.5", training of these intense rain rates can still overwhelm soils to produce runoff and flash flooding. The most likely areas for any flash flooding would be where the intense rates move across urban areas, but anywhere significant training occurs could cause instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!61cz0OYwMN1F0TylNYbCKX7aSfBlIVSc6hD0bHB-8FNYaU74DVqPRpAVRd_a8o2PA27P= gBrBa95JtcpHqswNCkRwL3Y$ for graphic product... ATTN...WFO...AKQ...CAE...ILM...LWX...MHX...RAH...RNK... ATTN...RFC...MARFC...SERFC...NWC... LAT...LON 38437637 38437604 38377581 38047578 37367581=20 36267605 35527626 34847658 34247751 33957848=20 33777922 33777972 33878010 34038023 34548032=20 35987953 38147708 38377672=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .